Problem with multicast audio streaming

[pftech]

Hi there,
I'm pretty new into multicast.
In a multimedia school lab I've implemented a multicast audio streaming using VLC so the master computer will stream cd audio to all other client computers (about 30 pcs).

Everything works great using RTP audio streaming in multicast, we just have a problem when master computer stops streaming (maybe just to change audio cd or just a pause), in all the clients we keep earing about 4-5 secs of audio in an endless loop (till we play stop on client's VLC).

I've tried a lot of settings even with buffers but nothing seems to fix this problem.

Anyone can help us?

Our VLC server config line is:
"C:\Program Files (x86)\VideoLAN\VLC\vlc.exe" -vvv cdda:///E:/ --sout #duplicate{dst=rtp{dst=239.0.0.10,port=5004,sap,name=lab.sdp},dst=display} :sout-keep

Thanks in advance for help!

Paolo